1. Field of the Invention
The present invention generally relates to steam generator sludge removal systems and more particularly to such systems for use in the secondary side of the steam generator.
2. Description of the Prior Art
Buildup of sediment or sludge on the secondary face of the tube is sheet in a boiler or steam generator has been proven to contribute to degradation of the tube material. It is a common practice to lance the tube sheet, and tube support plates with high pressure water to wash the sludge from between the tubes to a suction pickup where it can be removed from the steam generator. Most re-circulating steam generators have a wide lane that separates the hot leg tubes from the cold leg tubes. A wand that contains high pressure nozzles is inserted into this lane and the sludge forced out to the area between the steam generator shell and the tube bundle, called the annulus. From the annulus the sludge is easily washed to a suction pickup and removed from the steam generator.
In some recirculating steam generators and in Once Through Steam Generators (OTSG's) the geometry of the tube bundle does not permit lancing to be efficiently performed from a lane in the tube bundle. These generators must be lanced either totally or partially from the annulus.
The current method of lancing and inspection from the annulus uses a device that is pulled around the tube bundle with cables. These cables have frequently damaged tubes by abrasion-around the outside of the tube bundle.